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We collected fluvial suspended sediments in Fukushima after the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident and analyzed the 137Cs concentration in bulk and size-fractioned samples to investigate the particle-size-dependent distribution of radiocesium. The 137Cs concentration in bulk suspended sediments decreased from August to December 2011, possibly reflecting a decrease of radiocesium concentration in its source materials. Smaller particles had higher radiocesium concentrations, reflecting larger specific surface areas. Silt- and sand-size fractions occupied more than 95 % of the total 137Cs in the suspended sediments. The contribution of clay-size fractions, which had the highest 137Cs concentration, was quite small because of their low frequency. A line of the data showed that the particle size distribution of radiocesium was essential to evaluate the migration and distribution of radiocesium in river systems where radiocesium is mainly present as particulate form after the FDNPP accident.  相似文献   

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Journal of Radioanalytical and Nuclear Chemistry - Tokatsu area was on one pathway of the radioactive plumes released in the Fukushima Daiichi Nuclear Power Plant accident and absorbed dose rate in...  相似文献   

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We analyzed fresh and dead leaves collected in forests in Fukushima after the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, using autoradiography. Both fresh and dead leaves of Cryptomeria japonica were contaminated by radionuclides (134Cs and 137Cs). Contamination of the fresh leaves was possibly attributed to interception of radionuclides by tree canopies, whereas the dead leaves indicated the direct deposition of radionuclides by fallout and/or washout of radionuclides intercepted by tree canopies. Translocation of radiocesium from a contaminated branch to new leaves growing after the FDNPP accident was not clearly observed, although transfer of radiocesium from leaf parts to male flowers occurred. Fallen leaves of Quercus serrata, which started growing after the FDNPP accident, did not show radioactivity, indicating that significant amounts of translocation from other parts to new leaves did not occur. Fallen leaves of Q. serrata collected from a litter showed hot spots originating from direct fallout. Needles of Pinus densiflora were also contaminated by fallout. Leaching with pure water removed soluble fractions of radiocesium and hot particles from the surface of the contaminated leaves, but significant amounts of radioactivity remained. This means that foliar absorption occurred in both fresh and dead leaves. Further leaching experiments using surfactant and acetone could not remove the remaining radiocesium from the leaves. The leaching experiments indicate that radiocesium in the contaminated leaves is strongly fixed in leaf tissues and is not readily released unless leaf tissues are decomposed.  相似文献   

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Journal of Radioanalytical and Nuclear Chemistry - Determination of radionuclides transport characteristics is among the most significant research topics, which require extensive multidisciplinary...  相似文献   

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Concentrations of 134+137Cs and 133Cs in aquatic macrophytes, water, and sediment were measured in samples collected from Fukushima Prefecture, Japan. The concentrations of 137Cs in submerged and floating-leaved plants were higher than the values for emergent plants according to their main Cs uptake mode. The geometric mean water-to-plant concentration ratio for 137Cs and 133Cs was comparable observed in submerged and floating-leaved plants, while the geometric mean sediment-to-plant concentration ratio for 137Cs in emergent plants was higher than that of 133Cs, which suggest that the mobility of Fukushima accident-derived 137Cs is not in steady state 4–5 years after the accident.

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Isotopic composition of transuranic nuclides, with emphasis on Cm isotopes, were measured for environmental samples such as dust samples (black substances) from the roadsides and litter samples heavily contaminated by the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. Low levels of 238Pu, 239,240Pu, 241Am, 242Cm and 243,244Cm were determined by α-spectrometry after radiochemical separation. These results, including radioactive Cs, provided an isotopic data set. When the activity ratios among these transuranic nuclides were compared with those of core inventories (Units 1–3) in the FDNPP estimated by the JAEA group, fairly good agreement was found, indicating that traces of transuranic nuclides, probably in the forms of fine particles, were released into the environment without their large fractionations. The obtained data may lead to more accurate information about the on-site situation (e.g., burn-up, conditions of fuel during the release phase, etc.), which would be difficult to receive otherwise, and on the dispersion and deposition processes of transuranic nuclides and the behavior of these nuclides in the environment.  相似文献   

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